The sign of Cancer rules the middle part of the body. From the breasts to the rib cage, this is the area you want to feature.
No need for cleavage bearing tops, however. A flattering neckline can bring attention without seeming too desperate for that kind of attention.
If you're proud of your midsection, think about a flattering belt to draw the waist in, or even a peplum top, which flares out at the hips and makes your middle seem tiny. Whatever your style, there's a way to be proud of this aspect of your physical self.